The invention relates to methods and compositions for promoting wound healing. In particular, the invention provides cyanoacrylate polymer sealants in combination with biologically active agents including silver and insulin.
Normal wound healing involves the complex orchestration of a series of interrelated cellular events and cytokine cascades (Pierce, G. F. and Mustoe, T. A., Ann. Rev. Med., 46:467-481 (1995); and Martin, P., Science, 276:75-81 (1997)). The principle phases of wound healing consist of formation of a fibrin clot, followed by infiltration with inflammatory cells and fibroblasts, generation of granulation tissue and angiogenesis, wound contraction, and re-epithelialization. Growth factors and cytokines are supplied first by degranulating platelets, and later by fibroblasts and inflammatory cells, principally neutrophils and macrophages. The inflammatory response plays an active part in wound healing. If macrophage infiltration is prevented, wound healing is seriously impaired.
Currently, there are numerous methods and compositions available to treat wounds and to promote wound healing. A wound may constitute a variety of insults or damage to external body tissues, for example, a wound may involve a laceration, cut or scrape, surgical incision, sore, thermal burn, puncture, or decubitus ulcer, e.g., bed sores. Wounds can be classified in one of two general categories, partial thickness wounds or full thickness wounds. A partial thickness wound is limited to the epidermis and superficial dermis with no damage to the dermal blood vessels. A full thickness wound involves loss of the dermis and extends to deeper tissue layers and involves disruption of the dermal blood vessels. The healing of the partial thickness wound occurs by simple regeneration of epithelial tissue. Wound healing in full thickness wounds is more complex, involves multiple cell types (Martin, Science, 276:75-81 (1997)), and three stages. The first stage involves an immediate inflammatory response (2-5 days post wounding), followed by a proliferative phase (2 days-3 weeks) where no blood vessels (angiogenesis) and collagen are generated in the wound bed, resulting in the formation of granulation tissue. Contraction and re-epithelialization of the wound also occur during this phase. Finally, a maturation phase occurs during which collagen in the wound is subject to turnover and remodeling, ultimately resulting in the formation of scar tissue.
Intact epidermis serves as a mechanical barrier to infection. Due to the extensive tissue loss or damage in full thickness wounds, infection of more likely than in partial thickness injuries. Not properly cleaned and treated, a full thickness wound may, in severe cases, result in the development of a life-threatening infection.
A large number of dressings, bandages, and topic medicaments are available for the treatment of wounds. These products fall into two categories, passive and active. Passive wound dressings are dressing which serve only to provide mechanical protection and a barrier to infection. The dressings themselves do not supply any composition which enables or facilitates the healing process of the wound. Examples of passive dressings include gauze and adhesive bandages. Active dressings are dressing which supply some biologically active compound to the site of a wound. One type of active dressing is a dressing or wrapping which delivers or has been impregnated with antimicrobials (e.g., Bacitracin).
Another family of dressings which contain both passive and active properties are the hydrogels or hydrocolloids. Although many of these dressings do not supply any biologically active compound to the wound, they are specifically designed to create a moist environment around the wound to promote wound healing. Hydrogel and hydrocolloid dressings have been formulated to antimicrobials to help prevent and/or treat infection. However, to date, hydrogels or hydrocolloids have not been formulated with components that actively promote wound healing.
It has been suggested that the topical application of biological compounds may play an active role in wound healing. These compounds include mitogens, cytokines, growth factors, and hormones (e.g., PDGF, EGF, xcex2-FGF, GM-CSF, IGF-I, TGF-xcex1, and TGF-xcex2). However, there are limitations to these therapies. First, it is difficult to regulate the dosage of such an application. A liquid or viscous paste containing these components applied to a wound will tend to spread away from the site of the wound, or will be absorbed by and removed from the wound by dressings which are placed over the wound. Dressings which come in contact with the wound surface may also interfere with the normal healing process. Furthermore, these compounds are all polypeptides, they are extremely susceptible to rapid degradation following there application. Such degradation can occur from the contact of the polypeptides with proteases produced by bacteria normally on the surface of the skin. In addition, these agents may lack specificity in there action, and have adverse pleiotropic effects on adjacent tissues other than those tissues involved in wound healing.
In some cases, abnormal wound healing represents a significant health risk to patients. In particular, diabetic patients often experience slow and/or incomplete wound healing that may result in other serious consequences. Diabetes mellitus (DM) is a metabolic disease resulting from defective glucose utilization. A variety of molecular defects are implicated in the manifestation of type-I and type-II diabetes, including errors in insulin production, glucose transport, and glucose metabolism (Nathan, Scientific American Medicine (Dale and Federman, EDS.), Chapter 9, Section VI (1997)). Both type-I and type-II DM produce a variety of debilitating and life threatening complications, including degeneration of large and small blood vessels (i.e., macrovascular and microvascular disease) and increased susceptibility to infection. These two complications, unfortunately, make the DM patient prone to poor wound healing and wound infections. In extreme cases, limb amputation is necessary due to circulatory problems and infection at the site of wounds.
It has been proposed that insulin can be administered systemically or topically to help promote wound healing in diabetic and normal patients. The results described in the literature have been fairly inconsistent. Some studies have found that the topical application of insulin helps to promote wound healing (Hanam et al., The Journal of Foot Surgery, 22:298-301 (1983)) and others have found no significant effect by insulin on the rate of wound healing, particularly in decubitus ulcers (Gerber and VanOrt, Nursing Research, 28:16-19 (1979)). Two U.S. Pat. Nos. 5,145,679 and 5,591,709 have described the topical administration of insulin to a wound to promote wound healing. Both of these patents, however, describe the use of insulin in combination with glucose because the function of the insulin is to enhance the uptake of glucose and to thus promote wound healing.
The invention provides improved methods and compositions for promoting wound healing. In particular, the invention involves the use of cyanoacrylate polymer sealants in combination with therapeutics, such as silver and insulin, and related compositions. Cyanoacrylate polymers have previously been used to form sealants to close holes in tissue, or to replace or supplement sutures or as a hemostat. The cyanoacrylate can be applied to the skin as a liquid or gel to produce a protective barrier film. Although the prior art has suggested the use of cyanoacrylates alone, or sometimes in combination with antimicrobials (U.S. Pat. No. 6,001,345) the prior art has been limited. Prior patents have shown that most medications alter the performance of cyanoacrylates, either preventing them from setting or causing them to set so rapidly that they cannot be used to form protective films, see e.g. U.S. Pat. No. 5,684,042. Additionally, the prior art suggested that protein based medicaments could be expected to be inactivated by the protein binding properties of cyanoacrylates. The methods and products of the invention have overcome many of these prior art problems. In particular, a new way for formulating cyanoacrylate compositions to incorporate biologically active molecules has been discovered according to the invention.
In some aspects, the invention relates to a composition of a cyanoacrylate polymer sealant and silver and/or insulin incorporated within the cyanoacrylate polymer sealant. The silver and insulin retain biological activity even when formulated within the cyanoacrylate polymer sealant. The composition, even though formulated with biologically active agents, is capable of sealing tissue and promoting wound healing. In some embodiments, the composition includes insulin incorporated in the cyanoacrylate polymer, such that at least 50% of the insulin is biologically active. In other embodiments, at least 60, 65, 70, 75, 80, 85, 90, 95, 98, or 99% of the insulin is biologically active.
Preferably the cyanoacrylate polymer sealant is composed of a monomer which comprises a cyanoacrylate ester. In some embodiments, the cyanoacrylate ester is derived from a monomer having a side group alkyl chain consisting of 1-10 or 4-10 carbon atoms. In some embodiments, the alkyl chain is butyl, octyl, or decyl. A preferred alkyl chain is N-butyl. In yet other embodiments, the composition also includes a biocompatible plasticizer, such as, dioctyl phthalate. A polymerization inhibitor may also be added.
The silver incorporated within the cyanoacrylate polymer sealant may be any type of silver. For instance, the silver may be a sulfadiazene, a silver salt, or a solid metallic silver. In some embodiments, the solid metallic silver is colloidal silver. In other aspects, the invention relates to a method for enhancing wound healing by administering to a wound the composition of the cyanoacrylate polymer sealant having silver or insulin incorporated therein in an effective amount to enhance wound healing. In some embodiments, the silver is colloidal silver or metallic forms of silver. The metallic form is not restricted to any particular size or dimension or shape. Indeed, alternative forms of metallic silver are contemplated, including, but not limited to, such forms as microbeads, mesh, granules, grains, silver-coated fibers, or silver filings.
The invention further provides formulations in which additional reagents are used to supplement the polymerizable cyanoacrylate monomer and the silver or insulin. Such reagents may include solublization reagents, anti-polymerization reagents, pliability reagents, stabilization reagents, or any combination of these reagents.
In some embodiments, the composition is applied to the surface of the wound in a liquid formulation. In particularly preferred embodiments, at least one cyanoacrylate monomer and silver or insulin are combined and applied to a wound under conditions such that the cyanoacrylate monomer polymerizes and forms a cyanoacrylate-silver or insulin matrix over and within a wound. In still other embodiments of the methods, an additional step of monitoring the progress of wound healing is incorporated.
The invention in other aspects relates to a method for enhancing wound healing by administering to a wound an effective amount for enhancing wound healing for a cyanoacrylate polymer sealant and silver. In some embodiments, the silver is a silver mesh which may optionally be laid down directly over a wound and the cyanoacrylate is applied over the surface of the silver mesh under conditions such that the cyanoacrylate polymerizes. In other embodiments, the cyanoacrylate may be applied to the silver mesh in vitro and the cyanoacrylate/silver mesh may be applied or laid over the surface of the wound. In other embodiments, the silver is silver sutures and the sutures are used to close the wound and the cyanoacrylate is applied over the surface of the wound and sutures. In other embodiments dissimilar metals are used together, for instance, zinc and silver are used together.
In other embodiments of the method, a further step of applying a current across the silver to enhance flow into the wound is incorporated. The current may be applied using electrophoresis or any other method for applying current.
The method may also involve the application of insulin to the wound in addition to the silver. The insulin may be incorporated directly into the cyanoacrylate polymer sealant or, optionally, it may be injected directly into the wound or applied topically to the wound prior to the application of cyanoacrylate polymer sealant.
In yet other aspects, a method for reducing scar formation is provided. The method involves administering to a wound a cyanoacrylate polymer sealant and a compound selected from the group consisting of insulin and silver, wherein the combination of the sealant and the insulin or silver results in a synergistic reduction in scar formation. In some embodiments, insulin is administered directly to the wound. The direct administration may involve topical administration or injection. Optionally, the insulin may be incorporated in the cyanoacrylate polymer sealant. In other embodiments, the silver is administered directly to the wound. Alternatively, the silver may be incorporated in the cyanoacrylate polymer sealant.
In another aspect the invention is a method for enhancing wound healing in a hyperglycemic subject. The method involves administering to a wound a cyanoacrylate polymer sealant and a glucose antagonist in an effective amount for enhancing wound healing. In one embodiment the glucose antagonist is 2-deoxy glucose.
In yet another aspect the invention is a method for enhancing wound healing in a hypoglycemic subject. The method involves administering to a wound a cyanoacrylate polymer and a sugar in an effective amount for enhancing wound healing. In one embodiment the sugar is glucose.
In other aspects the invention relates to a method of preparing a cyanoacrylate adhesive containing a medicament. The method involves neutralizing or slightly acidifying the medicament, drying the solution, micronizing the medicament, and dissolved or suspending the medicament in the cyanoacrylate formulation. Preferably the medicament is insulin, a sugar, or a sugar antagonist. In one embodiment the medicament is adjusted to a pH of about 5-7.0 in solution. In other embodiments the moisture content is below 1000 ppm, and more preferably below 100 ppm.
In some embodiments the medicament is associated with a carrier such as sugars, polysaccharides or other biocompatible polymers such as polyvinyl pyrrolidone (PVP), sodium carboxymethyl cellulose (CMC) or gelatin. Optionally the medicament may be mixed into an aqueous solution of the carrier, wherein the amount of carrier is greater than the amount of medicament, bringing the solution to a pH between 5 and 7, and drying the solution. In one embodiment the carrier is a sugar oligomer such as trehalose.
In other aspects a composition prepared by the method described above is provided. In some embodiments the medicament is insulin.
Each of the embodiments of the invention can encompass various recitations made herein. It is, therefore, anticipated that each of the recitations of the invention involving any one element or combinations of elements can, optionally, be included in each aspect of the invention.